Professional Products LT1 Throttle Body - Waiting To Inhale

Installing Professional Products' 52MM LT1 Throttle Body

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Professional Products LT1 Throttle Body - Waiting To Inhale

At a street price of around $225 ($200 for the satin-finish version), Professional Products' polished 52mm LT1 throttle body offers top-tier looks and assembly quality for a comparatively modest sum. Ours came with fresh bolts and gaskets, along with two different throttle linkages to fit both the Corvette- and F-body-style LT1 engines.

A peek down the gullet of the new throttle body offers a good look at the convex area between the throttle bores. Like those bolt-in "airfoils" that were popular in the L98 days, this feature helps smooth the flow of air into the intake manifold.

If you're performing this installation yourself, begin by removing the intake tract ahead of the throttle body. It should come out as one piece, freeing up plenty of room for you to work. Remember to unhook the Air-Injection Reactor (AIR) and OptiSpark-vent tubes.

Disconnect the throttle linkage (top), followed by the harnesses for the Idle Air Control (IAC) and Throttle-Position Sensor (TPS).

If the TB's coolant lines are still connected (we bypassed ours in a previous issue), you'll need to unhook them as well.

Next, remove the four bolts that secure the throttle body to the intake manifold.

Even with the bolts out, the throttle body will most likely remain affixed to the intake. A sharp rap with your fist should break it loose.

Set the old throttle body aside, then use a razor blade to scrape away any gasket material that remains on the intake's mating surface.

Take care to prevent debris from falling into the intake bores.

Place the old throttle body on a bench or table, and remove the bolts that attach the IAC manifold.

Remove the manifold and set it aside.

Next, unbolt and remove the TPS. Set it aside, along with the round rubber insulator.

Now you're ready to transfer the IAC manifold to the new throttle body. (Be sure to use the fresh gasket that came with the kit.) With that done, install the TPS and insulator.

The finished product should look something like this.

To install the new throttle body on the car, simply reverse the teardown process. Before reattaching the air-intake tract, have a friend sit in the car and, with the engine off, fully depress the gas pedal. Verify that the throttle blades open completely, as shown above.

Reinstall the intake tract, reattaching the AIR and Opti-vent tubes along the way.

You may need to use a flathead screwdriver to gently stretch the intake bellows over the larger-than-stock throttle-body opening. Tighten the clamp securing the bellows to the throttle body, then fire up the car and check for air leaks. The engine may idle a bit roughly for a few moments, as the ECM adjusts to the additional airflow.

Here's a look at the engine with the new throttle body installed. Too bad the rest of the top-end hardware doesn't look this nice.

Having verified that our installation was leak free, AntiVenom honcho Greg Lovell strapped the car to the shop's in-house chassis dyno and made a pair of pulls. While the larger throttle body didn't add to our '96 coupe's peak output, it did boost horsepower by as much as 6 between 5,000 and 6,000 rpm. A post-install test drive also revealed throttle tip-in to be noticeably sharper, giving the car a more responsive feel in everyday driving. Perhaps most important, the extra airflow capacity offered by the 52mm throttle bores should help optimize the performance of the head-and-cam kit we have planned for the near future. More on that in an upcoming issue.

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